The present invention relates to a battery module and a temperature-controlling apparatus therefor, and more specifically to a battery module capable of effectively conducting the temperature control of each battery cell and a temperature-controlling apparatus therefor.
Widely used as energy sources for electric vehicles, etc. are wet-type secondary batteries which can be rechargeable by chemical reaction and thus repeatedly reusable. Such secondary batteries which may be called rechargeable batteries are exemplified by nickel-cadmium batteries (Ni--Cd batteries). Recently, higher attention has been paid to nickel-hydrogen batteries which have higher energy density than the nickel-cadmium batteries. In the nickel-hydrogen batteries, nickel or nickel hydroxide is used as a positive pole, and a metal hydride (hydrogen storage alloy) is used as a negative pole.
In such a wet-type rechargeable battery, the battery efficiency decreases as the temperature increases. Accordingly, heat generated in charge and recharge cycles should be removed as much as possible.
One example of an apparatus for cooling such a battery is schematically shown in FIG. 10. In FIG. 10, a battery 101 comprises a rectangular battery casing 104 having an inlet opening 102 for a cooling medium on a front side thereof, an outlet opening 103 for the cooling medium on a rear side thereof, and a plurality (2.times.4 in this example) of battery modules 105 disposed in the battery casing 104. In the figure, connections between each battery module 105 are omitted. Each battery module 105 is constituted by two sets of assemblies each composed of a plurality (5 in this example) of rectangular battery cells 106, which are bound integrally. Each battery cell 106 is connected in series via connection plates 107.
In such a temperature-controlling apparatus, the cooling medium introduced through the inlet opening 102 flows between the battery modules 105 in the battery casing 104 and is discharged through the outlet opening 103.
The battery module 105 used in the above apparatus has a structure as shown in FIG. 11. Among battery cells a-j in the battery module 105, battery cells a-d disposed on both ends are well cooled by the cooling medium due to good contact therebetween, while battery cells e-j disposed inside the battery module 105 are not well cooled. Thus, it may be considered to provide a gap between adjacent battery cells, but such a structure would lead to the easy deformation of the battery cells when internal pressure increases in each battery cell in the process of charging or recharging. In order to prevent such deformation, a casing of the battery cells should be thick, which in turn results in an undesirable increase in the weight and volume of the battery module.
On the other hand, to prevent a decrease in initial potential of the wet-type rechargeable battery in cold areas or in the winter seasons, the battery should be warmed. In such a case, a heated medium should be introduced into the battery casing through the inlet opening thereof in order to uniformly heat the battery cells.